The invention relates to a nut-runner with a power arm and a reaction arm constructed preferably as a casing, each of which is controlled in one end region so as to be pivotable relative to each other about a common axis, with a geared clamp wheel which is mounted in a drilled hole in the first end region of the power arm so as to be rotatable about the axis, and with a catch mounted on the power arm interacting with this clamp wheel, said catch being in the engaged position when the power arm pivots in one direction, in which position said latch engages with the teeth of the clamp wheel, and slips over the teeth of the clamp wheel when the power arm pivots in the other direction, and with a hydraulic power cylinder consisting of a cylinder and a piston which acts between the two arms in the vicinity of their other end regions.
In this nut-runner, previously known from DE-OS No. 30 08 381, the clamp wheel, the power arm encompassing the clamp wheel, and the reaction arm, which completely encompasses the power arm, are positioned concentrically from the interior outward. For this purpose the reaction arm, also constructed as a casing, has in its first end region an opening which runs concentrically relative to the axis and in which the circular first end region of the power arm is led to the exterior. Because of these three elements, positioned concentrically and as sleeves, the distance between the internal opening of the clamp wheel and the exterior of the reaction arm in the area of the first end region of the latter is rather large. In other words, a relatively great amount of clearance is required around a nut or screw on which the hexagonal recess of the clamp arm is mounted for it to be possible to mount the nut-runner referred to in the foregoing. Nut-runners such as those referred to above are typically used for bracing flanges. The clearance around a tensioning nut or screw of such a flange connection is determined in part by the distance to the next screw or nut, but this clearance typically is even greater than the space remaining free radially inward. In the case of a flange connection of pipes, for example, the effort has been made to reduce to the minimum the distance between the tensioning screws and the outer wall of the pipes to be connected, and the radial clearance is correspondingly small.
The untoleranced dimension of the state-of-the-art nut-runner described in DE-OS No. 30 08 381 is determined by the external diameter of the first end region of the reaction arm. This untoleranced dimension is always the same, regardless of the clamp wheels employed. In the case of the state-of-the-art nut-runner, the untoleranced dimension is still justifiable when the clamp wheel with the largest hexagonal recess is used, but becomes disadvantageously large when the clamp wheel with the smallest hexagonal recess is used. To remedy the situation, a special nut-runner would have to be produced, at least for all current widths across hexagonal nuts. This, however, would entail heavy expense for manufacture, storage, and use. Consequently, nut-runners are normally manufactured for a certain range of nominal widths across within which the clamp wheels required may be used. But in this case the goal of keeping the untoleranced dimension about as large for all widths across flats as it is in the case of eyebolt wrenches cannot be reached.
It is consequently the aim of the invention to avoid the disadvantages of the state-of-the-art nut-runner described in DE-OS No. 30 08 381 and to improve the nut-runners of the type discussed in the foregoing by making the untoleranced dimension smaller, and in particular by causing it to fall within the range of that of a conventional eyebolt wrench.
This problem is solved on the basis of the nut-runners of the type previously discussed, in that the reaction arm encompasses the clamp wheel through a maximum of 180 degrees and the arms engage by way of a circular guide positioned concentrically relative to the axis, extending over a maximum of 180 degrees, and consisting of a guide groove and a projection, this guide being positioned between the axis and the second end region of the arms.
The decisive difference relative to the state-of-the-art nut-runner described in DE-OS No. 30 08 381 lies in the circumstance that the power arm is no longer mounted in a circular opening in the reaction arm, and thus the guide between power arm and reaction arm does not extend through 360 degrees; this guide is rather positioned between the axis and the second end regions of the arms and extends through a maximum of 180 degrees. As a result, the reaction arm no longer encompasses the power arm (as with the state-of-the-art nut-runner); it rather ends above a line running transversely to the longitudinal direction of the reaction arm and through the axis. The untoleranced dimension of the nut-runner as thus described, especially the radial untoleranced dimension, is thus no longer determined by the external dimensions of the reaction arm, being determined exclusively by the circular free end of the power arm.
In a preferred further development of the invention it is now proposed that the power arm be detachably connected to the reaction arm, so that the power arm can be simply replaced. In contrast to previously known nut-runners, the clamp wheel is no longer replaced in order to change the width across the flat; the unit is removed from the clamp wheel and power arm instead. This has the decided advantage that, regardless of the size of the reaction arm (which is constructed preferably as a casing), the untoleranced dimension on the free end of the power arm is always the smallest possible dimension relative to a specific width across a flat. In other words, the untoleranced dimension is determined essentially by the size of the clamp wheel, on the basis of replacement of the power arm. The overall advantage is achieved that a single casing of a nut-runner, in which it is also advisable to house the power cylinder, can be outfitted for different widths across and the smallest possible untoleranced dimension per width across is achieved.
The embodiment of the nut-runner claimed for the invention can be achieved with a nut-runner as described in DE-OS No. 30 08 381, the power cylinder in this case being mounted preferably in the reaction arm, to permit designing the component made up of power arm and clamp wheel, inclusive of the catch, as simply as possible. In an especially preferred further development, a nut-runner as described in DE-OS No. 34 07 126 is used, in which a more or less pear-shaped power arm is provided the smaller drive coupling of which is located inside the cylinder bore and catches in a recess in the piston, the axial line of the cylinder bore running transversely to the longitudinal direction of the power cylinder. In the case of this nut-runner the reaction arm is designed as a casing and consists preferably of a casing component and of bearing boxes that can be fastened to the side of this casing component by simple means, in which bearing boxes the guide for the power arm is formed. To replace a power arm it is necessary only to remove these bearing boxes, after which the power arm may be extracted from the casing component. As a result, power arm replacement is rendered especially simple.